ES2345375A1 - Apparatus and process for extracting sulfur compounds from a hydrocarbon stream - Google Patents

Abstract

Disclosed is an apparatus and process for extracting sulfur compounds from a hydrocarbon stream. A prewash section for converting hydrogen sulfide to a sulfide salt by reaction with an alkali such as caustic communicates with an extractor section disposed directly above the prewash section for converting mercaptans to mercaptides by reaction with alkali. Hydrocarbon product exits the extractor section through a coalescer that prevents alkali from exiting with the hydrocarbon product stream. A prewash section for converting hydrogen sulfide to sodium sulfide by reaction with an alkali such as caustic prepares the hydrocarbon stream for extraction. Spent alkali is continuously withdrawn and regenerated alkali is continuously added to the prewash section.

Description

Apparatus and procedure for extracting compounds of sulfur from a stream of hydrocarbons.

Background of the invention

This invention generally relates to a procedure and an apparatus for the removal of compounds from Organic sulfur from a stream containing hydrocarbons. In In particular, it refers to the use of an aqueous caustic solution for Remove mercaptans from a hydrocarbon stream.

So far the conventional practice is to try Acid hydrocarbon and gas streams to eliminate mercaptans. Extraction procedures are typically used when treat light hydrocarbons and gaseous streams for the Elimination of mercaptans. Mercaptans have been eliminated traditionally of hydrocarbon streams due to its aroma smelly.

US 5,244,643 B1 describes a process by which a stream of hydrocarbons that includes mercaptan sulfur, air and aqueous alkaline solution that includes a mercaptans oxidation catalyst mixed in a mixing vessel in which mercaptans are converted to disulfides The effluent separated from the top of the container of mixture is decanted in a container providing streams separated from air, liquid hydrocarbon product containing disulfide and an aqueous alkaline solution that includes catalyst mercaptan oxidation.

US 4,562,300 B1 describes putting in contact a hydrocarbon stream that includes mercaptans organic with sodium hydroxide to release hydrocarbons from organic mercaptans The caustic solution rich in mercaptans is oxidizes with a catalyst and organic mercaptans become in organic disulfides. The regenerated caustic solution mixture free of organic mercaptans and organic disulfides enters a decanter in which the organic disulfides and the caustic solution A stream of hydrocarbons from which they have extracted upstream mercaptans mixed with solution regenerated aqueous caustic containing small amounts of organic disulfides to extract organic disulfides from the regenerated caustic solution. These procedures leave disulfides. in the liquid hydrocarbon stream. Government regulations future and current considers increasingly undesirable to leave organic disulfides in a hydrocarbon product stream liquids

In an extraction procedure liquid-liquid, disulfides are removed from the hydrocarbon stream to not be returned. In J. R. Salazar, HANDBOOK OF PETROLEUM REFINING PROCESSES 9-4 - 9-5 (Robert A. Meyers ed. 1986) describes a general liquid-liquid extraction procedure. In a typical extraction procedure, a current is fed of liquid hydrocarbons to an amine absorption column for contacting it with an amine, such as diethylamine, to absorb acid gases such as hydrogen sulfide and carbon dioxide carbon from the hydrocarbon stream. The current of hydrocarbons depleted in hydrogen sulfide and other gases acids undergo prewash in a prewash container that it contains liquid soda from 6.5 to 7.0% by weight to convert the remaining hydrogen sulfide to sodium sulfide which is soluble in caustic soda. The hydrocarbon stream, now without sulfur from hydrogen, undergoes a countercurrent flow of liquid soda 14% by weight in an extractor vessel. Jet dishes in the extractor container facilitate countercurrent contact. The mercaptans in the hydrocarbon stream react with soda providing mercaptures Mercaptures in the stream of Hydrocarbons are soluble in soda. A stream of hydrocarbons poor product in mercaptans happens in head from the extraction column through a settling tank at a sand filter container and the mercapuro-rich soda passes from the bottom of the column. The settling tank allows to decant and compensate for rapid variations in the level of Soda in the sand filter. The sand filter agglutinates the soda for that can descend by gravity to the bottom of the container while the product hydrocarbon stream passes out of the container through an outlet that is protected in the upper part to prevent the admission of soda drops descending Mercapturo-rich soda receives an injection of air and catalyst when it passes from the extraction column to an oxidation vessel for regeneration. Oxidation of disulfide mercaptides using a phthalocyanine catalyst Regenerates the caustic solution. A disulfide separator receives the Disulfide-rich soda from the oxidation vessel. The separator of disulfide evacuates excess air and decants disulfides from the soda before the regenerated soda is drained and returned to the extractor bowl Disulfides run through a filter of sand and are removed from the procedure.

Hydrogen sulfide must be removed in the prewash container before extraction or the soda will react preferably with the hydrogen sulfide in the container extractor and will leave mercaptans in the hydrocarbon stream. Finally, the soda in the prewash container is overloaded with sulfides and must be replaced to ensure a conversion adequate hydrogen sulfide. In the extraction system of mercaptans described above, the soda in the container Prewash has to be replaced in each batch. Therefore, the hydrogen sulfide conversion at the end of the cycle of Replacement is minor. The prewash container also has to be great to ensure a proper mixture of soda and hydrocarbon. On the other hand, the conventional extraction system Mercaptanos uses four containers: the container of soda prewash, extraction vessel, storage tank Settling and sand filter container. Each container must have its own support and base structure that makes the construction of this system involves a high investment of capital.

Therefore, an object of the present invention is to combine the extraction vessel, the reservoir of Settling and sand filter container in a container for reduce the capital required to build a system Extraction On the other hand, an object of the present invention is combine the soda prewash container, the container extractor, settling tank and filter vessel sand in a container to reduce capital necessary to build an extraction system.

Summary of the invention

The authors of the invention have developed a procedure and an apparatus to combine the functions of the extractor container and sand filter container in a common extractor bowl. A coalescence separator is provided at the top of the container extraction section for provide the function that the sand filter had previously provided. The coalescence separator can be separated from a plate of upper jets in the extractor section by one volume enough to compensate for rapid variations in the level of bland and provide the function of a settling tank.

The authors have also developed a procedure and an apparatus for combining the functions of the prewash vessel, the extraction vessel, the settling tank and the sand filter vessel in a common extractor vessel. Directly above a section of prewash with soda is a section of
extraction.

The authors have also developed a provision that provides for the continuous disposal of spent soda of the prewash section with soda and the continuous replenishment of the soda regenerated to the prewash section of a system extraction of mercaptans.

Other objects, achievements and details of this invention can be obtained from the following description Detailed of the invention.

Brief description of the drawings

Figure 1 is a process flow scheme for the process of the present invention.

Figure 2 is a detailed outline of the extraction vessel of Figure 1.

Figure 3 is a perspective view of a feed plate in an extractor section of the present invention.

Figure 4 is a perspective view of a jet plate of an extractor section of the present invention.

Detailed description of the invention

With reference to the Figures you can obtain a general understanding of the procedure and apparatus of this invention. Referring to Figure 1, a liquid stream of hydrocarbon such as LPG or naphtha containing sulfur mercaptan and hydrogen sulfide is fed through a pipe 10 to a 12 amine absorber vessel. Amines such as diethylamine or monoethylamine are fed to the amine absorber vessel 12 at through a pipe 14. The amine absorber vessel 12 It contains a series of dishes. The pipe 10 that supplies the hydrocarbon stream has a distributor that is below of the midpoint of the container 12. A nozzle in the pipe 14 to supply the amines is arranged towards the bottom of the container allowing counter-current contact of the amines that descend into the container and the hydrocarbon that ascends through the container 12. The amines in the container 12 They react with hydrogen sulfide to provide thiolamines. From typical form, a hydrocarbon stream that contains approximately 1000 to 2000 ppm by weight of hydrogen sulfide is reduces up to 15 ppm by weight of hydrogen sulfide concentration in the container 12 amine absorber. From the bottom of the an amine absorber vessel 12 flows an effluent stream of amine rich in thiolamines through a pipe 16 while the hydrocarbon effluent flows out of the top of the container 12 amine absorber through a pipe 18 with a substantially reduced concentration of hydrogen sulfide. In addition, carbon dioxide or other acid gases that possibly are present in the feed stream in the pipe 10 also react with the amines and are absorbed in the effluent stream of amines leaving the amines absorber vessel 12 to through the pipe 16.

A soda recycling line 20 joins the pipe 18 to allow an aqueous alkaline solution such as aqueous soda and hydrocarbon effluent from container 12 amine absorber mix in a pipe 22 before entering the extraction vessel 24. A differential indicator controller Pressure (PDIC) 26 maintains a pressure drop across a control valve 28 such as 7 to 103 kPa and preferably 28 to 55 kPa to ensure a proper mixture between liquid soda and the liquid hydrocarbon in the pipe 22.

The premixed hydrocarbon stream and the aqueous soda enters the extraction vessel 24 through the pipe 22. The extraction vessel 24 comprises a section 30 of lower prewash and an upper extractor section 32 separated by a dividing partition 34 convex down no Perforated. The extractor section 32 is directly above of prewash section 30 and both sections share preferably at least one common wall 33. Section 30 of prewash includes a coalescence separator 36 near the part upper section 30 prewash. Pipe 22 feeds the prewash section 30 near the bottom of section 30 Prewash

In prewash section 30, an aqueous alkaline solution such as soda of 3 to 20 ° Baume (2 to 12% by weight), suitably 5 to 17 ° Baume (3 to 12% by weight) and preferably 8 to 12 ° Baume (5 to 8% by weight) reacts with all remaining hydrogen sulfide to provide a sulfide salt such as sodium sulfide. Typically, the aqueous alkaline solution is 10 ° Baume (7% by weight). The higher density aqueous soda and the sulphides dissolved therein descend by gravity towards the bottom of the prewash section 30 while the hydrocarbon with the spent hydrogen sulphide ascends toward the top of the prewash section 30. Coalescence separator 36 serves to bind together small droplets of soda that rise in prewash section 30 giving them a sufficient weight to begin descending through prewash section 30 with the rest
of the soda.

A transfer conduit 38 has a communication in communication with the prewash section 30 next to the upper part of prewash section 30 above the coalescence separator 36 and an outlet in communication with the extractor section 32 near the bottom of section 32 of extractor. The higher density soda pushes the hydrocarbon of lower density up through conduit 38 of transfer without the need of a pump. A pump 42 pumps the soda spent outside the bottom of section 30 of prewash through recycle line 20. The spent soda is eliminates through the recycle duct 20 through a pipe 44 regulated by a control valve 46. The flow of soda through control valve 46 is automatically controlled by a level indicator controller (LIC) 48 that regulates the level of soda in section 30 of prewash at the hydrocarbon interface - bland. The LIC 48 that detects the level of soda in section 30 of prewash emits a regulation signal for the control valve 46 relative to fully opening to bring the level of soda in the prewash section 30 to the pre-selected desired level. By consequently, the spent soda is continuously removed from the prewash section 30 through pipe 44 through the 20 recycling duct. The spent soda removed through the pipe 44 can be sent to a soda degassing chamber spent (not shown) that allows volatile hydrocarbons to eliminate by evaporation in the upper part of the chamber before that the spent soda descend out of the chamber for the treatment. The soda regenerated in a pipe 50 is fed continuously to the soda recycling line 20 and therefore to the prewash section 30 at a flow rate regulated by a valve control 52 governed by a flow controller (FRC) 98. In addition, water is added to the soda recycling line 20 through a pipe 54

An aqueous alkaline solution such as soda aqueous in the extractor section 32 has a concentration of 17 to 25º Baume (12 to 19% by weight), preferably 18 to 22º Baume (13 to 16% by weight) and typically 20º Baume (14% by weight). A Sulfide-free hydrocarbon stream of hydrogen exits through the outlet of the transfer conduit 38 to the extractor section 32.

The mercaptans in the extractor section 32 react with the soda by providing sodium and water mercaptides. The lower density hydrocarbons ascend to the top of the extractor section 32 while the aqueous soda and mercaptides dissolved in the aqueous soda sink to the bottom of the extractor section 32 where it collects them in the convex partition wall 34 down not perforated. The hydrocarbon rises to the coalescence separator 58 comprising a 61 cm crosslinked layer that causes the smaller soda droplets to clump toward the top of the oil extractor section 32 due to its smaller size. Coalescence separator 58 binds smaller soda droplets together to form larger droplets that will tend to sink back toward the bottom of the extractor section 32. The treated hydrocarbon substantially depleted in mercaptans and mercaptides leaves the extractor section 32 through conduit 60
product.

The spent soda rich in mercaptides is separated through a drain in the upper part of the partition dividing 34 convex down through a pipe 62. The pipe 62 actually extends through section 30 of prewash above coalescence separator 36 and through its common wall 33.

A pipe 64 adds oxidation catalyst to the pipe 62. This invention does not require the use of a catalyst of oxidation of specific mercaptans. They are known in the art. Many suitable catalysts. A preferred class of catalyst It comprises sulfonated metal phthalocyanine. A metallic phthalocyanine preferred sulfonated is highly cobalt phthalocyanine monosulfonated prepared by the process of US document 4,049,572 B1, the description of which is incorporated herein as reference. Other phthalocyanine catalysts are described in US 4,897,180 B1. Other dipole type catalysts that They are suitable for use in alkaline contact solution is described in US 4,956,324 B1; US 3,923,645 B1; US 3,980,582 B1 and US 4,090,954 B1. Typically, the catalyst for oxidation in the aqueous alkaline solution will have a concentration of 10 to 500 ppm by weight and preferably a concentration of 200 ppm in weigh. The soda stream spent with added catalyst is preferably heated in an indirect heat exchanger with low pressure current as heat exchange fluid in a heater 66. Heater 66 preferably heats the soda aqueous spent from 38 ° C to 43 ° C. To the stream of spent soda in the pipe 62 through a pipe 68 to form a pipe 70 of oxidizer feed sufficient air is added to oxidize The Mercaptures The mixture of spent aqueous soda and air is distributes to an oxidation vessel 72. In the container 72 of oxidation, sodium mercaptides react catalytically with oxygen and water providing soda and organic disulfides. A Rashig ring filling in the oxidation vessel 72 increases the surface area in it improving contact with the catalyst. An outlet duct 74 separates the effluent from a upper part of the oxidation vessel 72. The effluent of oxidation vessel 72 comprises three phases that include a air phase, a liquid disulfide phase and a soda phase aqueous liquid

The outlet duct 74 carries the effluent from the oxidation vessel 72 to a disulfide separator 76 which it comprises a vertical section 78 and a horizontal section 80. A once decanted in the separator, the air phase leaves the part top of vertical section 78 through a pipeline 82. The two liquid phases are decanted in horizontal section 80 of the disulfide separator 76. The lightest disulfide phase leaves by the upper part of the horizontal section 80 through a pipe 84. The disulfide effluent from disulfide separator 76 it is transported by pipe 84 to a sand filter 86 to agglutinate and separate any trace of soda and is removed from the process through a pipe 88. The heaviest regenerated soda comes out from the bottom of the horizontal section 80 through the pipe 90. The vertical section 78 of the disulfide separator 76 Includes carbon Rashig rings to increase surface area such that the liquid trapped in the air is separated and prevents exit through the pipeline 82. A portion of the section horizontal 80 of disulfide separator 76 includes anthracite carbon to serve as a coalescence separator. Soda Droplets contained in the disulfide phase will melt into larger droplets and more heavy that will fall to the heaviest aqueous soda phase to exit at the entrance to pipe 90 instead of at the entrance to the pipe 84.

The pipe 90 that carries regenerated soda is It divides into two pipes 92 and 50. Pipe 92 has regenerated soda to the extractor section 32 at a flow rate regulated by a valve 94 of control governed by a flow controller (FRC) 96. The pipe 50 carries regenerated soda to the soda recycling line 20 at a flow rate regulated by the control valve 52 governed by the FRC 98. FRC 96 and 98 measure the flow of soda in their pipes 92 and 50 respective and send a signal to control valves 52 and 94, a regulation relative to fully open to obtain a flow desired input. The desired input flow is determined to obtain a desired concentration of soda in the respective section of the extraction vessel 24.

The pressure in the absorber vessel 12 of amines and in the extraction vessel 24 is maintained by regulating the hydrocarbon flow from the extractor section 32 in the product duct 60 via a governed control valve 61 by a pressure gauge controller (PIC) 63 that regulates the pressure in the product duct 60. The pressure will remain preferably at a level that ensures that the hydrocarbon remains in a liquid state. This pressure typically varies from 517 to 2758 kPa. The temperature of the hydrocarbon streams is maintained preferably at a temperature of 38 ° C. He heater 66 raises the temperature of the spent soda preferably from 38 ° C to 43 ° C before it enters the oxidation vessel 72 in the pipe 70. The reaction of oxidation is exothermic which results in an increase in the effluent temperature in the outlet duct 74 preferably not exceeding 57 ° C. Therefore, the temperature in the separator 76 of disulfide will preferably be less than 57 ° C. The pressure on the oxidation vessel 72 and in disulfide separator 76 are preferably maintains 345 to 448 kPa in line 82 by a control valve 85 regulated by an indicator controller of pressure (PIC) 87 that controls the pressure in the pipeline 82.

Figure 2 shows the inside of the extraction vessel 24 in greater detail. Section 30 of Prewash is substantially empty with some exceptions. A pipe outlet 22 extends to a distributor 26 which Dispenses upward feed from it. He distributor 26 comprises a cylindrical pipe perpendicular to the pipe 22 with openings directed upward at 45 ° above the horizontal An interface 57 soda-hydrocarbon it is typically located between the distributor 26 and the separator 36 of coalescence. Coalescence separator 36 comprises a 30 cm thick reticulated layer near the top end that extends across the entire cross-sectional area of section 30 of prewash An inlet 38a to the transfer conduit 38 arranged above coalescence separator 36 supplies fluid to through an outlet 38b to distributor 56 in section 32 of extractor. An inlet to the pipe 72 extends through the prewash section 30 above separator 36 of coalescence

Figure 3 shows the internal part of the extractor section 32, in combination with Figure 2. The distributor 56 comprises a cylindrical pipe that extends perpendicular to the outlet 38 of the transfer conduit 38 which communicates with the distributor 56. Openings arranged towards down to 45º below the horizontal admit food to the extractor section 32. The distributor 56 is arranged on a feed plate 102 comprising a horizontal plate 104 that extends partially across the cross sectional area 32 extractor and two overflows 106 vertical 106 and 108. The distributor 56 is arranged in a feed tray 109 defined by overflows 106, 108, plate 104 and a surface internal wall 33 common section 32 exhaust fan extractor container 24. A drop tube 110 has an outlet 112 arranged in an input tray 107 defined by the plate 104, overflow 106 and the internal surface of the common wall 33 of the extraction vessel 24.

Figure 2 shows six plates 120 of jets above feed plate 102. They can be used more or less jets 120 of jets in the extractor section 32 of the present invention. Suitably, 2 to 15 dishes are used in a section of Extractor and are typical of 6 to 8 dishes. In addition others are contemplated types of structures to facilitate liquid-liquid contact, such as stuffed beds or trays.

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Reference is made to Figures 2 and 4 for Describe 120 jets of jets. Each plate 120 of jets includes an output tray 122 defined by a surface internal of the common wall 33 of the extraction vessel 24, a horizontal tray plate 124, which communicates with an input 126 of the descent tube 110, and a vertical overflow 128. The plates 120 jets also include a plate 129 comprising a perforated sieve section 130 and an unperforated section 131. The unperforated section 131 is separated from sieve section 130 by an overflow 134 vertical. An input tray 132 is left defined by the unperforated section 131, the inner surface of the common wall 33 and the overflow 134. The regenerated soda of the pipe 92 is fed to the plate 120 input tray upper jets.

It can be seen in Figure 3 that the vertical overflows 106, 108 extend along the rope through extractor section 32 defining tray 107 of input and feed tray 109. In Figure 4 you can appreciate that vertical overflows 128, 134 extend as far as length of the rope through the extractor section 32 defining the input tray 132 and the output tray 122. The height of the overflows 106, 108, 128 and 134 is 30.5 cm so that when the soda exceeds 30.5 cm level, it spills over its overflow respective. The height of the overflows can be made greater. At feed plate 102, the soda that spills from the tray 107 input and feed tray 109 spills into down to interface 111 soda-hydrocarbon by under feed plate 102. In the case of dishes 120 of jets, the spilled soda flows over the sieve section 130 to come into contact with the hydrocarbon that rises through the perforations in section 130 sieve. The soda that goes to the tray 122 of the outlet of the jets 120 runs through from the inlet 126 of the descent tube 110 to the trays 132, 107 inlet of the underlying jet plate 120 or the plate 102 of supply, respectively, through output 112. This arrangement ensures adequate contact between the hydrocarbon and the soda while the hydrocarbon rises to the top of the extractor section 32 and exits through the duct 60 of product.

Coalescence separator 58 is close to the top of the extractor section 32 above the 120 jet dishes. The coalescence separator 58 comprising a crosslinked layer extends throughout the entire area cross section of the extractor section 32. It is important that the coalescence separator 58 is of sufficient quality so that no allow the passage through more than 2 ppm of soda and preferably not more than 1 ppm of soda because it is the last barrier that prevents soda from leaving the product hydrocarbon. Is suitable a coalescence separator such as COALEX of Koch-Otto-York.

Coalescence separator 58 is separated of the upper jet plate 120 to provide a volume 59 of open decantation between them to act as an element of compensation in the case of rapid variation in the level of soda. He volume 59 of settling occupies at least enough volume as to accommodate a plate 120 more jets. The separator 58 of coalescence and decant volume 59 in container 24 of Extraction avoids the need for sand filter and containers Decanting in extraction procedures conventional liquid-liquid.

Claims (10)

1. An apparatus (24) for converting compounds of sulfur in a hydrocarbon stream, said said comprising apparatus: a prewash section (30) to convert hydrogen sulfide to a sulfide salt; a hydrocarbon feed line (22) with an entry in communication with said section (30) of prewash; a section (32) of extractor to convert mercaptans to mercaptides, said section being arranged extractor directly above said section (30) of prewash; a hydrocarbon conduit (60) product with an outlet in communication with said extractor section (32); Y a conduit (38) having an entrance in communication with the prewash section (30) and an exit in communication with the extractor section (32).

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2. Apparatus according to claim 1, wherein said extractor section (32) includes a separator (58) of coalescence on its upper part. 3. Apparatus according to claims 1 and 2, in which a container (24) includes said extractor section (32) and said prewash section (30). 4. Apparatus according to claim 3, wherein said extractor section (32) and said prewash section (30) they are separated by a partition wall (34) not perforated. 5. A procedure to convert compounds of sulfur in a hydrocarbon stream comprising: feed a stream of hydrocarbons that contains sulfur compounds to a prewash section (30) that contains alkali to convert hydrogen sulfide to a salt sulfide; separate a pre-washed hydrocarbon stream of said prewash section (30); feed said hydrocarbon stream prewash to an extractor section (32) to convert mercaptans in mercaptides, said extractor section being directly by above said prewash section (30); Y remove an extracted hydrocarbon stream containing mercaptides of said extractor section (32).

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6. Method according to claim 5, in which said hydrocarbon stream must pass through a separator (58) of coalescence before being removed from said section (32) of extractor. 7. Method according to claim 5, which It also includes: mix a stream of hydrocarbons and a alkaline current to provide said current of hydrocarbons containing sulfur compounds; continuously withdraw an alkaline current depleted containing sulfides of said prewash section (30); Y recirculate at least part of said current alkaline depleted for mixing with said stream of hydrocarbons, continuously adding an alkaline stream regenerated to said prewash section (30).

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8. Method according to claim 7, in which a portion of said spent alkaline current is recirculated to said prewash section (30) and another part of said stream Exhausted alkaline is removed from said alkaline current out of stock 9. Method according to claims 7 and 8, wherein said regenerated alkaline current is added to said alkaline current exhausted. 10. The apparatus (24) according to the claims 1 and 2 comprising: an alkali recirculation duct (20) with an entry in communication with the container (24) to remove the alkali of the container and an outlet in communication with the container; an alkali addition pipe (52) in communication with said alkali recirculation conduit (20); Y an alkali separation pipe (44) in communication with said alkali recirculation conduit (20).